共查询到20条相似文献,搜索用时 15 毫秒
1.
Rene Bellwied 《Acta Physica Hungarica A》2004,21(2-4):199-205
Nuclear suppression factor and u 2 measurements as a function of transverse momentum for neutral strange particles are shown and compared to particle identified spectra from PHENIX and WA98 and to models that attempt to describe the suppression of particles at moderate pt in central RHIC Au?Au collisions. It is shown that identified spectra carry additional information to the published charged particle spectra. In particular, dependencies of the R AA and u 2 values on the measured particle species will be discussed in the context of several models. 相似文献
2.
Matthew Wysocki 《The European Physical Journal C - Particles and Fields》2009,62(1):103-107
This is an overview of the PHENIX J/ψ results in hot nuclear matter from heavy ion collisions. Current results for R
AA and v
2 in Au+Au collisions, as well as R
AA from Cu+Cu collisions are included and discussed. A comparison is also done to cold nuclear matter effects using R
dAu results. 相似文献
3.
J. Bielcik 《The European Physical Journal C - Particles and Fields》2007,49(1):375-378
The strong suppression of high pT hadrons observed at RHIC has led to the interpretation that energetic partons lose their energy via induced gluon radiation
in the hot and dense matter before fragmenting into hadrons. The study of heavy quark production can extend our understanding
of this scenario. Due to the dead cone effect, the suppression of heavy quark mesons at high pT is expected to be smaller than that observed for charged hadrons at the same energy. The measurement of non-photonic single
electrons up to high pT provides information on charm and beauty production. The semi-leptonic decays of D and B mesons are the dominant contribution
to the non-photonic electron spectra. The preliminary spectra from p+p, d+Au and Au+Au collisions at =200 GeV have been extracted for mid-rapidity non-photonic electrons in the range 1.5<pT (GeV/c)<10. The corresponding nuclear modification factors (RAA) are presented and show a large suppression in central Au+Au collisions, indicating an unexpectedly large energy loss for
heavy quarks in the hot and dense matter created at RHIC. This observed suppression is compared to recent theoretical models.
PACS 13.85.Qk; 13.20.Fc; 13.20.He; 25.75.Dw 相似文献
4.
Debasish Das 《Pramana》2012,79(4):863-866
The study of formation of heavy quarkonia in relativistic heavy-ion collisions provides important insight into the properties of the produced high-density QCD medium. Lattice QCD studies show sequential suppression of quarkonia states with increasing temperature; which affirms that a full spectroscopy can provide us a thermometer for the matter produced under extreme conditions in relativistic heavy-ion collisions and one of the most direct probes of deconfinement. Muons from the decay of charmonium resonances are detected in ALICE experiment in p?+?p and Pb+Pb collisions with a muon spectrometer, covering the forward rapidity region (2.5?<?y?<?4). The analysis of the inclusive J/?? production in the first Pb+Pb data collected in the fall of 2010 at a centre of mass energy of $\sqrt{s_{\rm NN}}=2.76$ ?TeV is discussed. Preliminary results on the nuclear modification factor (R AA) and the central to peripheral nuclear modification factor (R CP) are presented. 相似文献
5.
B. Sahlmuller 《Indian Journal of Physics》2011,85(6):981-985
The π
o meson has been a crucial probe for observing jet quenching in ultrarelativistic heavy-ion collisions at RHIC. Measurements
of the η meson in the same collisions have also shed light on a possible dependence of the observed suppression on the particle species.
The preliminary π
0 nuclear modification factor R
AA
from the 2004 RHIC run allowed a first systematic comparison between a precise measurement with high statistics and theoretical
calculations, constraining model parameters such as the initial gluon density dNg/dy, and the transport coefficient [^(q)]\hat q. The final π
0 spectra and R
AA
are shown as well as the first η results obtained with both PHENIX electromagnetic calorimeters. 相似文献
6.
I. Kraus H. Oeschler K. Redlich 《The European Physical Journal C - Particles and Fields》2007,49(1):109-113
Considering particle production in heavy-ion collisions, a particular role has been attributed to strange particles because
strangeness was predicted to be a sensitive probe of the properties of QCD matter. The statistical model is very successful
in describing the chemical composition of the final state of collisions over a wide range of incident energies. However, without
an additional strangeness undersaturation factor, γS, hadron gas models hardly reproduce the data from small colliding systems nor from reactions at the smaller collision energies.
Here we investigate the influence of an alternative assumption, exact strangeness conservation in small subvolumes of the
fireball, on the model predictions. Therefore, we introduce strangeness equilibrated subvolumes. The canonical strangeness
suppression in these correlated clusters accounts successfully for the smaller production of strange particles. The system
size dependence of the correlation volume and of the thermal parameters are presented. 相似文献
7.
8.
J. Bielcikova 《The European Physical Journal C - Particles and Fields》2007,49(1):321-326
We present results on two-particle azimuthal correlations of neutral strange baryons (Λ, Λ̄) and mesons (KS
0) for pT=2–6 GeV/c associated with non-identified charged particles in d+Au and Au+Au collisions at =200 GeV measured by the STAR experiment. We investigate in detail the associated yield of charged particles as a function
centrality of the collision and transverse momentum of trigger and associated particles to look for possible flavor, baryon/meson
and particle/anti-particle differences. We compare our results to the proton and pion triggered correlations as well as to
a fragmentation and recombination model.
PACS 25.75.-q; 25.75.Gz 相似文献
9.
J. Zuo 《Indian Journal of Physics》2011,85(7):1131-1135
Di-hadron correlations will help understand the parton densities near jets traversing the medium, the process of hadron formation
and the di-hadron correlation away-side shape. We report on the di-hadron correlations between unidentified charged hadron
triggers with identified associated strange particles Λ and K
S
0) in Au+Au collisions at 200 GeV in STAR. Particle yields and ratios are extracted on the near-side and awayside of the trigger
particle. The baryon to meson ratios for associated particles as a function of Δϕ are also extracted. The shape of these ratios on the away-side is studied to understand the away-side’s pattern. The particle-type
composition in the hump regions in away-side is compared to that in the near-side peak. These ratios may help to elucidate
the particle composition in the away-side and near-side of the correlation pattern arising due to a fast parton traversing
the medium. 相似文献
10.
A. László 《Indian Journal of Physics》2011,85(6):787-791
Transverse momentum spectra up to 4.5GeV/c were measured around midrapidity in Pb+Pb reactions at ?{sNN }\sqrt {s_{NN} } = 17.3GeV, for π
±, p, [`(p)]\bar p and K
±, by the NA49 experiment. The nuclear modification factors R
AA
, R
AA/pA
and R
CP
were extracted and are compared to RHIC results at ?{SNN }\sqrt {S_{NN} } = 200GeV. The modification factor R
AA
shows a rapid increase with transverse momentum in the covered region. The modification factor R
CP
shows saturation well below unity in the π
± channel. The extracted R
CP
values follow the 200GeV RHIC results closely in the available transverse momentum range for all particle species. For π
± above 2.5GeV/c transverse momentum, the measured suppression is smaller than that observed at RHIC. The nuclear modification
factor R
AA/pA
for π
± stays well below unity. 相似文献
11.
12.
F. Laue 《The European Physical Journal C - Particles and Fields》2007,49(1):371-374
In relativistic heavy ion collisions, heavy flavor is expected to result predominately from initial hard parton–parton scatterings.
Hence, in the absence of later stage effects, the production of heavy flavor in A+A collisions can be viewed as a superposition
of N+N collisions. Measurements of v2 or RAA of heavy flavor (or their decay electrons) in A+A collisions violate the simple superposition picture and therefore present
themselves as probes of the medium formed in such collisions. On the basis of the measured v2 and RAA of non-photonic single electrons in A+A collisions at RHIC, we will investigate the interplay between these observables as
well as the restrictions they pose for charm and bottom production. 相似文献
13.
Edward Wenger 《Acta Physica Hungarica A》2006,27(2-3):271-274
The PHOBOS Collaboration has measured transverse momentum distributions of charged hadrons produced in Cu+Cu collisions at √s NN =200 and 62.4 GeV. The nuclear modification factor R AA N part is calculated relative to p+p data at both collision energies as a function of collision centrality. For the same number of participating nucleons, R AA N part is essentially the same in both systems over the full range of p Tthat is measured. In addition, we observe that within experimental uncertainties, the ratio of 200 GeV to 62.4 GeV Cu+Cu yields has only a moderate centrality dependence and is consistent with the value previously measured in Au+Au collisions for a broad range of p T. 相似文献
14.
B. G. Zakharov 《JETP Letters》2011,93(12):683-687
We perform a joint jet tomographic analysis of the data on the nuclear modification factor R
AA
from PHENIX at RHIC and ALICE at LHC. The computations are performed accounting for radiative and collisional parton energy
loss with running coupling constant. Our results show that the observed slow variation of R
AA
from RHIC to LHC indicates that the QCD coupling constant is suppressed in the quark-gluon plasma produced at LHC. 相似文献
15.
W. M. Alberico A. Beraudo A. Molinari M. Monteno M. Nardi F. Prino 《The European Physical Journal C - Particles and Fields》2011,71(6):1666
The propagation of the heavy quarks produced in relativistic nucleus–nucleus collisions at RHIC and LHC is studied within
the framework of Langevin dynamics in the background of an expanding deconfined medium described by ideal and viscous hydrodynamics.
The transport coefficients entering into the relativistic Langevin equation are evaluated by matching the hard-thermal-loop
result for soft collisions with a perturbative QCD calculation for hard scatterings. The heavy-quark spectra thus obtained
are employed to compute the differential cross sections, the nuclear modification factors R
AA and the elliptic-flow coefficients v
2 of electrons from heavy-flavor decay. 相似文献
16.
B. G. Zakharov 《JETP Letters》2013,96(10):616-620
The flavor dependence of the nuclear modification factor R AA in the pQCD calculations at LHC energies has been examined. The computations are performed accounting for radiative and collisional parton energy loss with running coupling constant. Our results show that the recent LHC data on the R AA for charged hadrons, D-mesons, and non-photonic electrons agree reasonably with the pQCD picture of the parton energy loss with the dominating contribution from the radiative mechanism. 相似文献
17.
P. Sorensen 《The European Physical Journal C - Particles and Fields》2007,49(1):379-382
In this talk I argue that a substantial fraction of the non-photonic electron suppression in Au+Au collisions could arise
as a result of an enhanced Λc/D ratio rather than purely from jet-quenching. At intermediate transverse momentum (2<pT<6 GeV/c), the baryon-to-meson ratio in Au+Au collisions is enhanced compared to p+p collisions. Since charm-baryon decays
produce electrons less frequently than charm-meson decays, the non-photonic electron spectrum is sensitive to the Λc/D ratio. I show the dependence of the non-photonic electron spectrum on the baryon-to-meson ratio for charm hadrons. As an
example, I assume that the Λc/D ratio is the same as the Λ/K0
S ratio. I show that even if the total charm quark yield in Au+Au collisions scales with the number of binary nucleon-nucleon
collisions (Nbin), the electron spectrum at 2<pT<5 GeV/c will be suppressed relative to Nbin scaled p+p collisions by as much as 20%.
PACS 25.75.-q; 25.75.Dw 相似文献
18.
An incoherent binary nucleon-nucleon collision model of AA collisions is presented for simulating particle production in cold nuclear matter. With a simple phenomenological parameter,
the mean nucleon energy loss fraction, this model yields pseudorapidity density distributions that are comparable to those
of experiment, as well as those of HIJING. Particle production data for a given binary collision is extracted from the PYTHIA
event generator. The nuclear geometry is described by the Glauber model. The preliminary R
AA
and R
CP
results are also presented and discussed, with a proposal that R
AA
be redefined. 相似文献
19.
L. Cunqueiro J. Dias de Deus C. Pajares 《The European Physical Journal C - Particles and Fields》2010,65(3-4):423-426
We show that several effects considered nuclear effects are not nuclear in the sense that they do not only occur in nucleus–nucleus and hadron–nucleus collisions but, as well, they are present in hadron–hadron (proton–proton) collisions. The matter creation mechanism in hh, hA and AA collision is always the same. The p T suppression of particles produced in large multiplicity events compared to low multiplicity events, the elliptic flow and the Cronin effect are predicted to occur in pp collisions at LHC energies as a consequence of the high density partonic medium obtained. 相似文献
20.
E. Kolbe K. Langanke F.-K. Thielemann 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):389-396
We study the influence of a strange axial vector form factor Gs of the nucleon on the neutrino-induced proton and neutron knockout of 16O. In particular, we calculate how much Gs≠0 might affect the recently proposed signal for supernova νμ and ντ neutrinos in the Superkamiokande detector. We discuss whether Superkamiokande might be able to determine the value of Gs in a hypothetical neutrino-beam experiment. Finally we comment on the possible effect Gs≠0 might have on neutrino-nucleus cross sections in the neutrino-driven wind model for the nuclear r-process.
Received: 30 April 1998 / Revised version: 10 August 1998 相似文献